mus: Add UserActivityMonitor.

components/mus/ws/test_utils.h

Index: components/mus/ws/test_utils.h
diff --git a/components/mus/ws/test_utils.h b/components/mus/ws/test_utils.h
index 19cb43215c0baa0fd70c3bcf27f6bb3a3beb409c..dc1075fc7d938d66392ff9338a61d6e5b39fc211 100644
--- a/components/mus/ws/test_utils.h
+++ b/components/mus/ws/test_utils.h
@@ -17,6 +17,7 @@
 #include "components/mus/ws/platform_display.h"
 #include "components/mus/ws/platform_display_factory.h"
 #include "components/mus/ws/test_change_tracker.h"
+#include "components/mus/ws/user_activity_monitor.h"
 #include "components/mus/ws/user_display_manager.h"
 #include "components/mus/ws/user_id.h"
 #include "components/mus/ws/window_manager_state.h"
@@ -67,6 +68,23 @@ class UserDisplayManagerTestApi {
 
 // -----------------------------------------------------------------------------
 
+class UserActivityMonitorTestApi {
+ public:
+  explicit UserActivityMonitorTestApi(UserActivityMonitor* monitor)
+      : monitor_(monitor) {}
+
+  void SetTimerTaskRunner(
+      scoped_refptr<base::SingleThreadTaskRunner> task_runner) {
+    monitor_->idle_timer_.SetTaskRunner(task_runner);
+  }
+
+ private:
+  UserActivityMonitor* monitor_;
+  DISALLOW_COPY_AND_ASSIGN(UserActivityMonitorTestApi);
+};
+
+// -----------------------------------------------------------------------------
+
 class WindowTreeTestApi {
  public:
   explicit WindowTreeTestApi(WindowTree* tree);